Pole tips for magnets



POLE TIPS FOR MAGNETS Filed Nov. 9, 1962 2 Sheets-Sheet 1 A TTO/ZNE Y June 8, 1965 l. 1. BOSWELL 3,188,531

POLE TIPS FOR MAGNETS Filed Nov. 9, 1962 2 Sheets-Sheet 2 BY I /1M ATTORNEY United States Patent 3,188,531 POLE TIPS FOR MAQNETS Ian Irvine Boswell, Newport Pagnell, England, assignor to Newport Instruments (Scientific and Mobile) Limited, Newport Pagnell, England, a British company Filed Nov. 9, 1962, Ser. No. 236,508 Claims priority, application Great Britain, Nov. 13, 1961, 40,523/ 61 15 (llaims. (Cl. 317--158) This invention relates to pole tips for electroor permanent magnets and it is more particularly concerned with an improved pole tip construction by which the orientation of the face surface of the pole tip may be adjusted relatively to the body or yoke of the magnet to which it is secured.

The invention has particular, although by no means exclusive, application to magnets for providing a highly homogeneous field, such as magnets for nuclear resonance absorption measuring devices. It is well-known that in order to produce such highly homogeneous fields it is necessary to use magnetically homogeneous material for the pole tips. In such devices, it is also necessary that the pole faces be lapped and polished optically fiat and then aligned parallel to one another to Within optical limits or otherwise accurately adjusted to obtain the optimum homogeneity of the field between the opposing poles.

The present invention is concerned with the alignment of the pole tip faces of such magnet for providing a homogeneous field. Various means are already known for effecting this alignment of the pole tip faces. In one method, steerable poles are used whereby the adjustment is made between the pole face and the body or yoke of the magnet, while a further method incorporates athreepoint alignment mechanism between one pole face and its pole tip, the other pole being fixed. These methods are disadvantageous in that they present problems of adjustment which it is an object of the present invention to overcome.

The present invention constitutes an improved orthogonal system of alignment and consists of an arrangement for the construction of pole tips of permanent or electro-magnets in which each pole tip of such a magnet is formed in two parts, one of which is integral with or rigidly secured to the associated magnet pole and the other of which having the pole face thereon is secured closely adjacent to the first part in a manner which permits controlled rocking movement thereof relative to said first part over a limited arc in a single plane lying at right angles to its pole face, so that by arranging the respective planes of rocking movement of the opposing pole tips to be at right angles to one another, the attainment of precise parallelism between the opposing pole faces can readily be effected.

In order that the nature of the invention may be more readily understood, one particular embodiment will now be described with reference to the accompanying drawings wherein:

FIG. 1 shows one of a pair of similar pole tips in axial section.

FIG. 2 shows the same pole tip in transverse section with the part carrying the pole face thereon removed.

FIG. 3 shows a general side elevational view of the complete magnet structure.

In the embodiment shown in the drawings each pole tip comprises a part in the form of a disc and provided with means such as shown at 11 for securing to the main pole body or the yoke of the magnet. This part It) is also provided around its peripheral edge remote from the magnet fixing side with an annular recess 12 formed with are-entrant chamfered inner surface 13. A further pole tip part 14, also in the form of a disc of the same 3,138,531 Patented June 8, 1955 diameter as the part 10, is formed with a similar peripheral recess 15 having a re-entrant chamfered inner surface 16 at the side adjacent the part 10, while on the opposite outwardly facing side this part 14 is formed with the requisite optically fiat pole face surface 17.

The mutually opposing surfaces of the parts 10 and 14 are mainly planar but one, that of the part 10, is provided with two slightly proud regions 18 lying near to the periphery and in a common transverse line which is at right angles to the diametral plane through the part 10 which includes the axis of a circular hole 19. These proud regions 18 may be fixed to the part 10 by means of suitable adhesive materials or by mechanical means such as brazing or welding. The latter is directed parallel to the axis of the disc part 10 into a further circular hole 20 drilled radially inwards from the outer edge surface. This hole 28 is counterbored and then screw-threaded with a righthanded thread of, say, 18 threads per inch as shown at 21 to receive a screwed plug 22. Such plug has a head 23 adapted for engagement with a suitable tool for effecting rotation thereof and is also provided with an inwardly directed, reduced diameter extension 24 which is screw-threaded with a left-handed thread of, say, 32 threads per inch.

The extension 24 is engaged in the correspondingly threaded bore of a slide block 25 movable axially within the hole 20 and provided with an inclined wedge surface 26 which co-operates with a chamfered end surface 27 of a plunger 28 slidable axially within the hole 19. The outer end of the plunger 28 forms an abutment providing, in combination with the regions 18, a three-point support for the pole part 14.

The two parts 10 and 14 are held in contact with one another by means of an encircling clamping ring M which is provided at suitable and preferably substantially equispaced intervals around its inner surface with inward projections 30 having a V-section groove therein adapted to mate with the V-section surface constituted by the surfaces 13 and 16. The ring 29 is split into two parts as indicated at 31 and is provided with a clamping screw 32 extending from one part to the other across one of the dividing slots, and a link plate 33 containing two holes 34 for holding pivot screws or bolts, and extending across the other dividing slot. The line of division is preferably located as shown to lie in the radial plane through the plunger 28.

In the operation of the arrangement described, with the clamping ring 29 secure but not tightly fixed in position, the plug 22 is rotated to move it in or out by its screwed connection with the part 10, the corresponding rotation of the threaded extension 24 causing axial movement of the slide block 25 whereby the wedge surface 26 thereon causes axial movement of the plunger 28 to displace the second part 14 by a rocking movement about a fulcrum constituted by the proud regions 18. By appropriate similar adjustment of the other pole tip which is arranged to have its rocking plane disposed at right angles to that of the first pole tip, the desired state of precise parallelism of the two opposing pole faces 17 may readily be attained. Thereafter each pole face is held in accurate position by suitable final tightening of the clamping screw 32 to contract the associated clamping ring projections 30 into gripping engagement with the surfaces 13 and 16.

In FIGURE 3 is shown a general view of the magnet structure illustrating the disposition of the two pole tips with their respective planes of adjustment lying at right angles to one another. The complete magnet structure is supported by a suitable framework 35 and consists basically of the body or yoke of the magnet 38 with the adjustable pole tip parts 14, the body or yoke 38 having associated with its energising coils 36 which may be 3 watercooled and which receive current via terminals $7 fixed on the framework 35.

This embodiment of the invention is not to be considered as limiting and various modifications may be made within the scope of the invention. One such modification consists of forming the screwed plug 22 and its extension 24 with threads of the same hand of rotation but of respectively different pitch dimensions in order to provide a more sensitive means of adjustment of the inclination angle for a given angular movement of the adjusting plug.

The clamping means may also be modified in that the clamping ring 29 may be split into two parts and be provided with two similar clamping screws instead of one screw and a coupling link, each screw extending from one part of the clamping ring to the other part across each of the dividing slots. In this embodiment the line of division is preferably located to lie at right angles to the radial plane through the plunger 28. a

It is also to be noted that the division of the clamping ring 29 need not be restricted to only two parts but that it may be further subdivided provided that suitable tightening means are used. Other forms of clamp may be used.

I claim:

1. Magnet apparatus comprising two magnet pole pieces disposed in substantially co-linear and mutually opposing relationship, said pole pieces having mutually opposing and spaced-apart end faces, a separate plate-form pole tip member on said end face of each of said pole pieces, each of said pole tip members having a planar pole face surface on the side facing the opposite pole piece, pivotal mounting means pivotally mounting each of said pole tip members adjacent said end face of the associated pole piece for pivotal movement about an axis disposed at right angles to the axis of said pole piece, and positlon control means for effecting controlled rocking movement of each of said pole tip members whereby the angle of inclination of said pole face surface of said pole tip member relative to a plane normal to the axis of said pole piece may be altered, theaxes of pivotal movement of the two opposing pole tip members being disposed at right angles to one another.

Z. Magnet apparatus comprising two cylindrical magnet pole pieces disposed in substantially co-linear and mutually opposing relationship, said pole pieces having mutually opposing and spaced-apart end faces, a separate disc-form pole tip member on said end face of each of said pole pieces, each of said pole tip members having an optically fiat pole face surface on the side thereof facing the opposite pole piece, pivotal mounting means pivotally mounting each of said pole tip members adjacent said end face of the associated pole piece for pivotal movement about an axis disposed at right angles to the axis of said pole piece, and position control means on each of said pole pieces for effecting. controlled rocking movement of each of said pole tip members whereby the angle of inclination of said pole face surface of said pole tip member relative to a plane normal to the axis of said pole piece may be altered, the respective axes of pivotal movement of the two opposing pole tip members being arranged at right angles to one another.

d. Magnet apparatus comprising two magnet pole pieces disposed in substantially co-linear and mutually opposing relationship, said pole pieces having mutually opposing and spaced-apart end faces, a separate plate-form pole tip member on said end face of each of said pole pieces, each of said pole tip members having a planar pole face surface on the side facing the opposite pole piece, pivotal mounting means for pivotally mounting each of said pole tip members with the side thereof opposite that of said pole face surface lying closely adjacent said end face of the associated pole piece, said pivotal mounting means providing for limited rocking movement about an axis disposed at right angles to and laterally displaced from the axis of said pole piece, and position control means on each of said pole pieces for effecting controlled rocking movement of each of said pole tip members whereby the anglev of inclination of said pole face surface of said pole tip member relative to a plane normal to the axis of said polerpiece may be altered, the axes of rocking movement of the two opposing pole tip members being disposed at right angles to one another.

4. Magnet apparatus comprising two magnet pole pieces disposed in substantially co-linear and mutually opposing relationship, said pole pieces having mutually opposing and spaced-apart end faces, a separate plateform pole tip member on said end face of each of said pole pieces, each of said pole tip members having a planar pole face on one side and a parallel planar surface on the opposite side, pivotal mounting means for pivotally mounting each of said pole tip members with said opposite side thereof closelyadjacent the said end face of the associated pole pieces, said pivotal mounting means providing for limited rocking movement about an axis disposed at right angles to the axis of said pole piece, position control means for each of said pole tip members for effecting controlled rocking movement of each of said pole tip members whereby the angle of inclination of said pole face of said pole tip member relative to a plane normal to the axis of said pole piece may be altered, the respective axes of rocking movement of the two opposing pole tip members being disposed at right angles to one another, and separate clamping means for securing each of said pole tip members in its adjusted inclined position.

5. Magnet apparatus comprising two magnet pole pieces each secured to a common yoke system with said pole pieces substantially co-linear and in mutually opposing relationship to one another, end faces on said pole tips in mutually opposing and spaced-apart relationship, a separate plate-form pole tip member disposed adjacent each of said end faces of said pole pieces, each of said pole pieces having at least one projection thereon in contact with the facing surface of the associated pole tip member to form a fulcrum for rocking movement of said pole tip member relative to said pole piece about an axis lying at right angles to the axial direction of saidpole piece, means yieldably urging each of said pole tip members towards the associated pole piece and adjustable abutment means between each of said pole tip members and the associated pole piece for altering the angle of inclination of said pole tip member relative to said pole piece by rocking movement about said fulcrum, the respective axes of pivotal movement of said pole tip members being disposed at right angles to one another. 7

6. Magnet apparatus comprising two magnet pole pieces each secured to a common yoke system with said pole pieces substantially co-linear and in mutually opposing relationship to'one another, end faces on said pole tips in mutually opposing, substantially parallel and spaced-apart relationship, a separate parallel-sided plateform pole tip member disposed adjacent each of said end faces of said pole pieces, each of said pole pieces having a pair of aligned projections in offset relationship to the centre of said member, said projections being in contact with the facing surface of the associated pole tip member to form a fulcrum for rocking movement of said pole tip member relative to said pole piece about anaxis lying at right angles to the axial direction of said pole piece, an adjustable abutment between each of said pole tip members and the associated pole pi ces at a position offset from the centre of said member in a direction opposite said projections means yieldably urging each pole tip member towards the associated pole piece and clamping means securing each of said pole piece members to the associated pole piece, the respective axes of rocking movement of said pole piece members lying at right angles to one another.

7. Magnet apparatus comprising two cylindrical mag- 1 net pole pieces each secured to a common yoke system with said pole pieces substantially co-linear and in mutually opposing relationship to one another, planar end faces on said pole pieces in mutually opposing, substantially parallel and spaced-apart relationship, a separate parallel sided disc-form pole tip disposed adjacent to and coaxial with each of said end faces of said pole pieces, each of said pole piece end faces having a pair of aligned projections in contact with the facing surface of said pole tip member to form a pivotal fulcrum for rocking movement of said pole tip member relative to said pole piece about an axis lying at right angles to the axialdirection of said pole piece, adjustable plunger means in each of said pole pieces, said plunger means forming a third projection on said end surface for contact with said 'pole tip member and means yieldably urging said pole tip member into contact with said projections on the associated pole piece.

8. Magnet apparatus comprising two magnet pole pieces each secured to a common yoke system with said pole pieces substantially co-linear and in mutually opposing relationship to one another, end faces on said pole pieces in mutually opposing, substantially parallel and spacedapart relationship, and adjustable pole tips on each of said end faces of said pole pieces, each of said pole tips comprising a member having a planar pole surface facing the corresponding pole surface of the opposite pole tip, said member being tiltably mounted for movement along an axis disposed at right angles to the axial direction of the associated pole piece and the respective pivotal axes of the two pole tips being disposed at right angles to one another.

9. Magnet apparatus comprising two magnet pole pieces each secured to a common yoke system with said pole pieces substantially co-linear and in mutually opposing relationship to one another, end faces on said pole pieces in mutually opposing, substantially parallel and spaced-apart relationship, and adjustable pole tips on each of said end faces of said pole pieces, each of said pole tips comprising a first parallel sided member detachably secured to the end face of the associated pole piece, two fixed projections on the side of said member opposite that facing said pole piece, a third and movable projection on said first parallel sided member at a position spaced from said two fixed projections, a second parallel side member mounted to lie in contact with said three projections, the side surface of said second member opposite that in contact with said projections being optically flat to form a pole face surface and means for adjusting said third projection to cause tilting of said pole face surface about an axis which lies at right angles to the axis of the associated pole piece, the respective tilt axes of the two pole tips being arranged at right angles.

10. Magnet apparatus comprising two cylindrical magnet pole pieces in substantially colinear and mutually opposing relationship, said pole pieces having their outward ends secured to a common magnet yoke system, the inner ends of said pole pieces having end faces of planar form in mutually facing, substantially parallel and spaced-apart relationship, a disc shaped pole tip member of constant thickness located adjacent each of said end faces of said pole pieces, each pole end face having two projecting and aligned regions on the surface to form a pivot fulcrum line, an adjustable plunger mounted in each of said pole pieces for movement in a direct-ion parallel with the axis of said pole piece and projecting beyond the end face thereof to form a third projecting region spaced from said two projecting regions, yieldable clamping means securing each pole tip member in contact with said projections of the associated pole piece and means for adjusting the position of each of said plungers thereby to impart rocking movement to said pole tip members about the said fulcrum line, the respective fulcrum lines of the two pole pieces lying at right angles to one another whereby the opposing pole facing surfaces of said pole tip members may be brought into precise parallelram.

11. Magnet apparatus comprising two cylindrical magnet pole pieces in substantially co-linear and mutually opposing relationship, said pole pieces having their outward ends secured to a common magnet yoke system, the inner ends of said pole pieces having end faces of planar form in mutually facing, substantially parallel and spacedapart relationship, and an adjustable pole tip assembly on each of said end faces of said pole pieces, each of said pole tip assemblies comprising a disc-shaped first part having an optically flat pole surface on one side, a discshaped second part secured with one surface in contact with said end face of the associated pole piece, said second part having two raised and aligned regions on the surface opposite that in contact with said pole piece to form a pivotal fulcrum line, a plunger mounted in said second part for movement in a direction parallel with the axis of said pole piece and projecting beyond the said end face having said two fixed projections to form a third and movable projection, yieldable securing means securing said first part in contact with said projections and means for adjusting the position of said plunger thereby to impart rocking movement to said pole tip member about the axial line of said fulcrum points, the respective fulcrum lines of the two pole tip assemblies lying at right angles to one another whereby the facing pole surfaces may be brought into precise parallelism.

12. A magnet according to claim 11 in which said means for effecting adjustment of said plunger comprises a pair of interconnected screwed members, one of said members being carried in a threaded hole drilled inwardly from the outer edge surface of the second part and the other of said screwed members engaging with a slide block moveable axially within an inward extension of said hole, said slide block being provided with an inclined wedge surface which cooperates with a chamfered end surface of said plunger which is arranged to be slid able axially in a further hole drilled in the face of the second part.

13. A magnet according to claim 12 in which said pair of interconnected screwed members comprise a screwed plug provided with a thread of one hand of rotation and an inwardly directed, reduced diameter extension provided with a thread of the opposite hand of rotation.

14. A magnet according to claim 12 in which said pair of interconnected screwed members comprise of a screwed plug and a reduced diameter extension, each provided with threads of the same hand of rotation but with respectively different pitch dimensions.

15. A magnet according to claim 11 in which said yieldable securing means comprise an annular recess having a re-entrant chamfered inner surface around the adj acent peripheral edges of said first and second parts and a contractable clamping ring disposed in said annular recess.

References Cited by the Examiner UNITED STATES PATENTS 1/62 Kane et al. 3l7158 9/62 Nelson 317-158 

1. MAGNET APPARATUS COMPRISING TWO MAGNET POLE PIECES DISPOSED IN SUBSTANTIALLY CO-LINEAR AND MUTUALLY OPPOSING RELATIONSHIP, SAID POLE PIECE HAVING MUTUALLY OPPOSING AND SPACED-APART END FACES, A SEPARATE PLATE-FORM POLE TIP MEMBER ON SAID END FACE OF EACH OF SAID POLE PIECES EACH OF SAID POLE TIP MEMBERS HAVING A PLANAR POLE FACE SURFACE ON THE SIDE FACING THE OPPOSITE POLE PIECES, PIVOTAL MOUNTING MEANS PIVOTALLY MOUNTING EACH OF SAID POLE TIP MEMBERS ADJACENT SAID END FACE OF THE ASSOCIATED POLE PIECE FOR PIVOTAL MOVEMENT ABOUT AN AXIS DISPOSED AT RIGHT ANGLES TO THE AXIS OF SAID POLE PIECES, AND POSITION CONTROL MEANS FOR EFFECTING CONTROLLED ROCKING MOVEMENT OF EACH OF SAID POLE TIP MEMBERS WHEREBY THE ANGLE OF INCLINATION OF SAID POLE FACE SURFACE OF SAID POLE TIP MEMBER RELATIVE TO A PLANE NORMAL TO THE AXIS OF SAID POLE PIECE MAY BE ALTERED, THE AXES TO PIVOTAL MOVEMENT OF THE TWO OPPOSING POLE TIP MEMBERS BEING DISPOSED AT RIGHT ANGLES TO ONE ANOTHER. 